Electric telephone



(No Model.)

-N. PARKS.

. 4 ELECTRIC TELEPHONE. No. 385,956 Patented July 10, 1888.

, Summer, Lyn-wanes M E Z fin/Cd) l i L 31 M C ll'o rncz o W W wmmwUNITED STATES P NT OFFicE.

NATHANIEL PARKS, OF DEANSVILLE, NEWYORK.

ELECTRIC TELEPQHOINE.

SPECIFICATION forming part0! Letters Patent No. 385.9 56, dated July 1o,1 838.

A ppiiratiou filed April 20. 1888. Serial K01271281- (No model.)

1'0 aZZ whom it may concern.-

lle itknown that I, NATHANIEL Plums, a citizen of the United States,residing in Deansville, in the eounty'of Oneida, in the State of NewYork, have invented certain new and useful Improvements in ElectricTelephones,

of. which the following is a specification.

The invention relates to the class of elcctrical apparatus employed fortransmitting and receiving vocal sounds.

' The object ofthe invention is to provide instruments which will causethe required variation in the strengthof an electric current under theinfluence of sound-waves or air-vibratlOUS,-'il6t ilCl of great or smallamplitude,and which will convert such variations orelectricalundulations into vibrations corresponding to the originalsound-wavcs with as little loss of energy as possible.

Heretofore it has been customary to occasion the undulatiousin theelectric current by causing it to traverse an artificial resistance, the

valucof-which is increased and diminished by and in accordance with thesound-waves. To

accomplish this two electrodes are connected in the circuit and heldagainst each other in such manner that their pressure and consequentresistance may be varied through the instrumentality of the sound-waves.When the sound-waves are very light, the variation in the pressure iscorrespomlinglysmall, and when the waves are caused by sounds which aretoo loud the electrodes are thrown'apart and a consequent mutilation ofthe electric undulation is caused, since the ilow of the current 'is-niomenl: :ily interrupted. The present invention aims to remove thisdefect and provide an instrument which will operate perfectly whetherthe sound waves be light or heavy.

In general terms, the in\-'cntion may be stated to consist in'mountingupon a diaphragm or other body responding to-the sound-wavesan electrodewhich extends in a direction a right angles to its direction of movementand passes between two other clectrmles, one of which is connecteddirectly with the source of elec trieity,while the other is connectedwit-h the same source through an artificial resistance.

. The central electrode is connected with the ance offered by 'thetwobranch circuits will be varied, the resistance'of one branch beingincreased as that of the other is diminished. At one limit of itsvibration the circuitof the battery will be for the most partor-entirely through the branch containing no artificial resistance. andtherefore the current will flow freely, since the pressure upon thecorresponding electrode will be suffieientr-to' canse very goodelectrical connection. Attire-other;

limit of vibration, however, the resistance of this circuit isincreased, or its connections may be entirely interrupted; butthecircuit remains through the branch containingnthe artificial resistance,thus allowing. a' cor-respondingly small current'to flow. a k

The receivinginstrument mayrwith advan-' tage be constructed with ai-inductorinmof which the primary coil is included inthecircuit of thebattery and wound upon a softiron core, to which the receiving-diaphragmis applied. The secondary coil leads'to the the main line.- The currentthroughthe pri- --mary coil will magnetize the core,"and thus dispensewith the necessity of employing a permanent'magnet, and from thisconstruction certain advantages, hereinafter pointed out, may bederived. V I f.

The accompanying drawing is a transverse section of thetrznismitter andthe receiver,

showing the circuit-connections in diagram Referring to the figure,A'represents the'case of the transmitter. In the frontot'the case thereis formed an opening, I), and beneath this tlierejis' placed thediaphragm B, which may be of anywe]l.-k.no,wnconstruction. -Upon thediaphragm, preferably-at or uear'itscenter, there is pl'a'ced'anelectrode, 0, whichis hcre'shown. as projecting from the diaphragm atright angles and having its end turnedat w an angle and passing betweentwoelectrodes, G and G. The central electrode-may be of metal and theouter electrodes of 'earbo'n,'or other suitable. materials may beemployed. The electrodes 0 and C? are "mounted upon yielding springs Eand E, and suitableadjust ing-screws, D and D are applied to thesprings, whereby the pressure of the outer electrodes against thecentral electrode, 0, may be regulated. Normally they should be adjustedso as to touch the central electrode lightly when at rest.

The electrode 0 is electrically connected by a conductor, 1, with'ouepole of a suitable battery or other source of electricity. (Shown at O.)The electrode 0' is connected by a con doctor, 2, through the primarycoil, 1?, of an inductioneoil. A conductor, 3, leading from this coil,isconnected with the remaining pole of the battery. The electrode 0 isconnected,

by a conductor, 4, through a resistance, 1%..

with the conductor 2. The secondary coil S of the inductorium has itsrespective terminals connected with the main line L L. The two coils arewound upon a core, I, of soft iron, applied to a diaphragm, J, and thisdevice constitutes a receiver.

The operation of the apparatus is as follows: \Vhen the instrument is atrest, a cur rent from the battery traverses the conductor 1 to theelectrode 0, thence through both the electrodes 0 and (7 and theconductors 2 and 4 to the primary coil of the indnctorium, and thence byway of the conductor 3 to the other pole of the battery. The core I thusreceives amagnetization, dependent upon the current through the primarycell. Any variations in this current will cause corresponding variationsin the magnetism of the core, and will also occasion induced currents inthe secondary coil S, and such induced current-s will be transmittedupon the line L.

Variations in t he primary current are caused in the following man nor:\Vhen lhediaphragm Bis moved toward the electrode 0', for instance, theelectrical contact of the electrodes 0 and 0' becomes more perfect, anda greater amount of current will flow through the coil 1?;The'diminulion'in the pressure between the electrodes C and G occurringat the same moment, or even the complete separation of these electrodes,will tend to cause but a slight reduction in the current, sincetheresistance R is sufficient to prevent nu'ich onrrentfrom flowing throughthe conductor 4. -*-Whcn the diaphragm is vibrated in the oppositedirection, the resistance between the electrodes (1 and 0 becomesgreater, and therefore the current is diminished. At the same time thepressure upon the electrodes 0 is increased, and the electrodes 0 and 0may even be separated, and

- yet the circuitof the battery will remain comductors tends to lessenthe magnetism of the core, and also acts upon the primary coil and tendsto oppose the battery-current, so that electrical undulations of greateramplitude are occasioned than would be the case were the core apermanent magnet.

I claim as my invention 1. In a telephonic transmitter, an electrode,

two other electrodes applied to opposite sides of the same, means forincreasing the pressure of the first-named electrode upon either one of,the other electrodes and at the same time diminish the pressure upon theother, branch circuits leading from the two outer electrodes, and anartificial resistance contained inone of the branch conductors.

2. In a telephonic transmitter, an electrode, two contact-electrodesapplied to opposite sides of the same, means for increasing the pressureof the first-named electrode upon either of the other electrodes and atthe same time diminishing the pressure upon the remaining electrode,branch circuits leading from the two contact electrodes, an artificialresistance contained in oneor" the branch conductors, and an inductoriumhaving its primary coil included in the circuit with said branchconductors.

3. A telephonic transmitter, consisting of an electrode, twocontact-electrodes applied thereto, means for causing the pressure ofthe first-named electrode upon the other two to vary inversely, twobranch circuits leading from the respective contact electrodes, and anartificial resistance contained in one of the branch circuits.

4. The combination, wit-Ir. a movable diaphragm and an electrode carriedor vibrated thereby, of two contact--electrodesmpplied thereto, thepressure against one electrode being increased as the pressure againstthe other is diminished, and vice versa, and an electric battery havingone pole connected with the first-named electrode and the other polewith the two contact-electrodes, and an artificial rcsistanee interposedbetween one of the contactelcctrodes and said battery.

5. The combination, with a movable diaphragm and an electrode carried orvibrated thereby, of two contact-electrodes applied thereto, thepressure against one electrode be" \Vitnesses:

B. W. HAMLIN FRANK l). LMU'AM.

ICC

